The details can be seen here, the gist of it is that the free month that comes with your copy ends tomarrow if you started playing on october 8th, If you started playing later than that your free month is based on your initial start date. Buying 12 months for the price of nine via legouniverse.com is the cheapest in the long term, and you get some free in game gifts, what these are I do not know yet.

Ive heard time cards are available for purchase, and that you can purchase time from a LEGO store but the represenative I asked suggested I buy it online to make sure I get the free gifts.